1. Field
Example embodiments relate to a photomask, for example, to a reflective photomask.
2. Description of the Related Art
Photomasks are widely used in manufacturing semiconductor devices. By transmitting through or reflecting a radiation from a photomask, an image may be formed on a semiconductor substrate. The radiation may be a light such as an ultraviolet light, a vacuum ultraviolet (VUV) light, a deep ultraviolet (DUV) light, or an extreme ultraviolet (EUV) light. The radiation may also be an X-ray radiation or an e-beam.
Among the various types of radiations mentioned above, EUV lights are effectively absorbed in most materials. Therefore, EUV light lithography, which uses EUV light as a light source and requires reflective photomasks for lithography, is well known as an advanced lithography technology, and reflective photomask for EUV light lithography has been widely used.
FIG. 1 shows a conventional reflective photomask 5 and a pattern formed on a semiconductor substrate 7 using the conventional reflective photomask 5.
Referring to FIG. 1, the conventional reflective photomask 5 may include a substrate 1, a reflective layer 2 formed on the substrate 1 to reflect EUV light, and a light absorption pattern 3 formed on the reflective layer 2. The light absorption pattern 3 may contain information regarding patterns to be transferred to the semiconductor substrate 7. The light absorption pattern 3 may absorb the incident EUV light. The EUV light may be incident or reflected from the reflective photomask 5 in a direction other than a perpendicular direction to a surface of the reflective layer 2. For example, EUV light may be incident or reflected from the surface of reflective layer 2 at an angle other than 90 degree. Accordingly, shadows may be formed as part of the incident EUV light may be blocked by the side walls of the light absorption pattern 3. As a result, the patterns S and L transferred to the semiconductor substrate 7 may be shifted in a predetermined direction, and this phenomenon is called a shadow effect.